The feasibility of Cassia fistula gum with polyaluminium chloride for the decolorization of reactive dyeing wastewater
In order to find a new environmental-friendly coagulant that can partially replace conventional polyaluminium chloride (PAC) which was shown to be toxic to aquatic environment, gum extracted from seeds of Cassia fistula Linn. (CF) was investigated in decolorization of reactive dyes Blue 19 (RB19) and Black 5 (RB5) using jar-test experiments. The optimal results showed that crude CF gum (at pH 10, initial dye concentrations (IDC) of 100 and 50 mg L-1, gum dosages 200 and 300 mg L-1, reaction time 30 and 45 min, and agitation speed 60 rpm) did not achieve high degrees of decolorization in RB5 and RB19 (55.7 and 62.0 %, respectively) as compared with PAC coagulant (97.2 and 94.4 %, respectively) at the same IDC and reaction time. Whereas when CF gum was used in combination with PAC, decolorization efficiencies of both dyes reached over 92 % at 40 % volume fraction of gum. These results indicated the potential of using CF gum as a ?green? coagulant or as a contributing factor to color removal of textile wastewater.